Currently, the script assumes that /dev/sda is a clean disk if it has no partitions or LVM usage. However, in some setups (e.g., booting with netboot.xyz and using a minimal FAT partition with a Tailscale key), the FAT partition is created directly on /dev/sda (without a partition table), which leads the script to incorrectly identify it as usable for pvcreate.

observed error:

Can't open /dev/sda exclusively.  Mounted filesystem?
Error opening device /dev/sda
Cannot use /dev/sda: device has a signature

Suggested fix

Enhance find_drives() to check for a filesystem signature even if there is no partition table, or reject drives like /dev/sda if they are mounted or used without a GPT/MBR scheme.